Plunger lift apparatus



plfi 2l, 1936.

H. w. FLETCHER PLUNGER LIFT APPARATUS Filed Jan. 16, 14934 I INVNToR.

A TTORNEYS.

Cil

Patented Apr. 2l, 1936 UNITED STATES PATENT OFFICE PLUNGER LIFT APPARATUS poration of Texas Application January 16, 19.34, Serial No. 706,811

8 Claims.

My invention relates to plunger lift devices wherein a swab plunger operated by pneumatic pressure is employed to move a load of liquid to the surface and there discharge said liquid.

In installing such an apparatus, it; is usually necessary, in order to obtain the greatest eiliciency of operation, to submerge the lower end of the eduction tube below the level of the liquid in the well a distance sufficient to assure a suflicient supply of oil for continuous operation. Also in wells having high bottom hole pressure, the liquid will ll the well to a comparatively high level even when the flow is slow. To place the tube at a level where continuous operation may be obtained, it is sometimes necessary to submerge the tubing to such a depth that the gas pressure available will not start the operation and lift the plunger with the excessive load which accumulates above the same. That is, the gaseous fluid pressure necessary to start the device to operating at that submergence is much in excess of that necessary to keep it operating after the head of liquid above the lower end of the tube has been lowered to its usual operating level. As restrictions are now customarily placed on the amount of production from each well, itv is necessary to close down operations from time to. time to preventl production above the amount allowable,l and each time the pump is idle the well iills up to so high a level that the usual fluid working pressure will not start. the plunger lift device to operating. It is, therefore, necessary to employ other means, such as a swab to lower the liquid level before the plunger lift device will begin to function.

It is an object of my invention to provide means whereby the fluid level in the well may be reduced by the pressure of the gaseous fluid available without employing other and higher pressures and without swabbing or other operations of that character.

I desire to employ, in combination with the plunger lift apparatus, a kick-olf valve or a plurality of such valves, whereby the load above the plunger may be reduced to such an extent as to allow the plunger lift device to. operate, and to adjust such valve or valves to close when the plunger lift device is in operation.

I aim to employ an air inlet above the plunger which will admit air to the tube and start an upward flow and thus float the plunger up to a level Where the load above it is not too great for the available air or gas pressure to lift.

I also desire to operate the device at comparatively low gas pressures in the casing so that (Cl. 10B-52) there need be no large excess of pressure in said casing over what is necessary to raise. the usual load of liquid in the tubing.

In the drawing herewith Fig. l is a central longitudinal section through a plunger lift device employing my invention.

Fig. 2 is an enlarged section through a control valve which may be employed with the invention.

My plunger lift device as here illustrated is the one now in common use. It has a well casing I equipped with a casing head 2 having alateral opening 3 for connectionwith a source of gas under pressure.

'I'he casing has a flanged connection 4 with a discharge head 5 having a lateral fluid outlet I5 for the liquid and gas from the well. The upper end of the discharge head is connected at 'I to the tubing extension I4 having therein a gate valve 8 and closed by a housing 9 having a cap I0; Within the housing is a tubular rubber shock absorber II, having a central passage I2 leading to an upper outlet pipe control-led by a hand valve 'I3 by which it is normally closed.

Theeduction tube I5 is supported at its upper end in the casing head by a flanged coupling I5, the outer flange on which is clamped between the casing head 2 and the discharge head 5. Above the coupling IS isa perforated discharge nipple Il. At the lower end of the tubing is a housing I8 in which is slidably mounted a stop plate. I9 perforated to allow flow of iiuid therethrough. Said plate is resiliently supported by a coiled spring 2l), acting as a shock absorber for the plunger. Said spring is supported upon a lower plug 2I having openings 22 therein for the well fluid.

The plunger 23 is the usual plunger now in common use and includes a tubular body, cylindrical on its outer surface, to lit freely within the tube 5. It has a valve 24 adapted to close the lower end of the plunger, but is normally supported in open position upon a support 26 through which the valve stem 25 projects. It will be noted that when the plunger falls to the bottom of the tube, the valve will be there closed by contact of the stem with the stop plate I9.

In the normal operation of the plunger lift device, the plunger valve will close as described when it reaches bottom. Gas from the well or fromv an outside source will accumulate within the casing and depress the liquid level and will soon enter below the plunger and raise it with its load of liquid to the surface where the liquid will discharge through the outlet 6. The plunger will pass the outlet and by entering the closed upper end of the tube will be stopped and the valve in the plunger will be forced open. The gas behind the plunger will escape and the plunger will fall with the valve open to the bottom. When the plunger reaches bottom the level of liquid will have risen to the desired level in the tubing and casing, and it will be necessary for the gas pressure in the casing to depress the liquid level in the casing outside the tube to obtain entrance at the lower end of the tube and below the plunger. Thus the pressures in the casing mustJ exceed the amount necessary to lift the load. Also when the pump is not operated for a period the liquid level attains a still higher point in the casing, so that the fluid pressure in the casing is not sufficient to depress the liquid level to where the air or gas can enter below the plunger and raise the load above it.

To overcome this diiiiculty I employ a control valve of simple construction to permit entrance of air or gas at a point in the tube above the plunger and thereby cause the liquid head in the tubing to be lowered to where the plunger will operate without the necessity of excessively high pressure in the casing.

Thus I place in the tube at a predetermined lever above the lower end, a control valve or, if necessary several spaced valves, each including a coupling 2l, threaded at its end to be connected in the tube. The walls of the coupling are thickened and provided with a plurality of longitudinal grooves 28. Midway of the ends of each of the grooves, the wall of the coupling has an opening 29, the outer side of which forms a seat for a valve 30. Said valve is connected by a screw 3l to the lower end of the leaf spring 32, the upper end of which is bent inwardly and secured to the coupling by screw 33. The valve and'spring are so adjusted that the valve will be held normally spaced from the seat to allow passage of fluid into the tube. Ihe valve is closed, however, when the pressure outside the tube eX- ceeds that within the tube by a certain desired diierential.

'I'hus after the discharge of each load the gaseous uid pressure in the tube will be mostly exhausted and the pressure outside the tube will be great enough in comparison with that in the tube to seat the valve and the pressure in the casing will tend to be conserved and will raise the level of liquid in the tube to a point where the valve 30 will again open due to equalization of pressures outside and inside the tube.

The reduction of fluid pressures in the Vtube when the exhaust takes place will allow a surge of the liquid again to a level where the amount of fluid pressure available could not raise the load above the plunger which falls through the liquid to its seat near the lower end of the tube. As the control valve 30 opens due to a decrease in the differential, the gas or air pressure upon the liquid level in the casing will force the liquid and then the air through the openings 29 and into the liquid. This will aerate and stretch the liquid column above the openings 29 until the liquid overflows at the surface, and the column becomes materially lighter. There will then be a flow of liquid inwardly at the lower end of the tube which willlift or float the plunger upwardly until it passes the openings 29. The air or gas will then enter through said openings below the plunger and it will be raised to the surface carrying with it the aerated liquid above it. In rising, the plunger not only clears the tube of the bubbly, aerated oil, or liquid upon which the air lift alone is ineiiicient, but it will clear the tube of paraftln or other material which might tend to ultimately clog the whole tube.

When the plunger reaches the top and allows the air o-r gas behind it to exhaust, it again falls and the operation is repeated. As wells such as these have a limited allowable production, a few vsuch strokes. or operations will produce all that enters at the lower end of the tube and bubbles through the oil below the plunger and soon starts the plunger and itsV load to the surface. When the plunger passes the control valve the pressures inside and outside will bey so nearly equal that the valves 30 will open and allow the air or gas to enter below the plunger and carry the load along to the surface.

Thus, even where the device operates in the usual manner, the control valve will be of value in the operation. For if the control valve were not present, the air or gas in the casing would have to be sufcient to continually depress the oil level to the bottom of the tube, and, as the oil enters with the air at the lower end of the tube, the pressure must be sufficient to force the air through the oil below the plunger. This additional pressure in most cases is great enough to be a material item. When the air can enter through the valve, however, considerably less pressure will be sufcient to operate the device.

It will be seen therefore that, although control valves are old in operating an ordinary air lift device, they serve a different and valuable purpose also in the operation of a plunger lift device. By their use air pressures necessary for operation may be greatly reduced. Further the'operation of the device may be initiated with comparatively low pressures of air or gas compared'with what would otherwise be required.

By this combination of plunger lift and kick-off valve I am enabled not only to start the device to operating with an excessive head of liquid in the well, but also, after the operation has started, the amount of casing pressure may be appreciably less. I. thus economize in the amount vof gas pressure necessary to operate the device and am enabled, where a compressor is necessary, to operate with a small and economical installation.

It will also be obvious that although only one control valve is shown and described, as many may be used as are necessary to'handle the production of the particular installation in which the invention is employed.

What I claim as new is:

1. In a plunger lift device, a well casing, an eduction tube therein, a plunger in said tube operable by the pressure of gaseous fluid to raise a load of liquid from the well, a valve in said tube spaced a predetermined distance above the lower end of said tube, said valve being resiliently supported in normally open position but adapted to close a lateral opening in said tube when the iiuid pressure outside the tube exceeds that within the same by a predetermined amount.

2. A plunger lift device including a well casing,

an eduction tube therein, said casing being closed about said tube at its upper end to provide a pressure chamber within said casing, a plunger movable by pneumatic pressure to raise a load of liquid from the lower end to the upper end of said tube and discharge said load, and means including an air inlet valve in said tube, to control the load of liquid which the plunger is required to carry.

3. A plunger lift device including a well casing, an eduction tube therein, said casing being closed about said tube at its upper end to provide a pressure chamber within said casing, a plungermovable by pneumatic pressure to raise a load of liquid from the lower end to the upper end of said tube and discharge said load, a valve in said tube controlling the passage of fluid from said casing to said tube, said valve being closed by a predetermined excess of fluid pressure outside said tube, whereby the head of liquid above said plunger may be regulated.

4. A plunger lift device including a well casing, an eduction tube therein, said casing being closed about said tube at its upper end to provide a pressure chamber within said casing, a plunger movable by pneumatic pressure to raise a load of liquid from the lower end to the upper end of said tube and discharge said load, and means to control the load of liquid which the plunger is required to carry, including a control valve in said tube spaced above the lower end of said tube to admit gaseous fluid to said tube and raise any excess amount of liquid to the surface.

5. A plunger lift device including a well casing, an eduction tube therein, said casing being closed about said tube at its upper end to provide a pressure chamber within said casing, a plunger movable by pneumatic pressure to raise a load of liquid from the lower end to the upper end of said tube and discharge said load, and a normally open valve controlling an opening in said tube at a point spaced a predetermined distance above the lower end of said tube, said valve being held open by a spring with a predetermined force and closed by a certain excess of pressure outside said tube.

6. A plunger lift device including an eduction tube, a plunger movable by pneumatic pressure below the same to lift a load of liquid to the surface in combination with a control valve therein spaced a predetermined distance above the lower end thereof, said valve being regulated to allow entrance of iluid therethrough to said tube, but adapted to close when the fluid pressure outside said tube exceeds that within the tube by a predetermined amount.

7. A plunger lift device including an eduction tube, a plunger movable by pneumatic pressure below the same to lift a load of liquid to the surface in combination with a control valve therein spaced a predetermined distance above the lower end thereof, said valve being regulated to allow entrance of fluid therethrough to saidtube and adapted to close when the head of liquid above said plunger is below a predetermined amount to be lifted by said plunger.

8. A plunger lift device including a well casing, an eduction tube therein, said casing being closed about said tube at its upper end to provide a pressure chamber within said casing, a plunger in said tube freely movable by pneumatic pressure from the lower end to the upper end of said tube, and an inlet for gaseous pressure fluid formed in said tube at a predetermined distance above the lower end thereof whereby gaseous pressure fluid may enter said inlet and cause an upward flow of the column of liquid above said inlet and a circulation of liquid upwardly from the lower end of the tube so as to float said plungerfrom said lower end up past the level of said opening.

HAROLD W. FLETCHER. 

